What is a luteinizing hormone (LH) levels test?
This test measures the level of luteinizing hormone (LH) in your blood. LH is made by your pituitary gland, a small gland located underneath the brain. LH plays an important role in sexual development and functioning.
- In women, LH helps control the menstrual cycle. It also triggers the release of an egg from the ovary. This is known as ovulation. LH levels quickly rise just before ovulation.
- In men, LH causes the testicles to make testosterone, which is important for producing sperm. Normally, LH levels in men do not change very much.
- In children, LH levels are usually low in early childhood and begin to rise a couple of years before the start of puberty. In girls, LH helps signal the ovaries to make estrogen. In boys, it helps signal the testes to make testosterone.
Too much or too little LH can cause a variety of problems, including infertility (the inability to get pregnant), menstrual difficulties in women, low sex drive in men, and early or delayed puberty in children.
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What is it used for?
An LH test works closely with another hormone called follicle-stimulating hormone (FSH) to control sexual functions. So an FSH test is often done along with an LH test. These tests are used in different ways, depending on whether you are a woman, man, or child.
In women, these tests are most often used to:
- Help find the cause of infertility
- Find out when ovulation occurs, this is the time when you are most likely to get pregnant.
- Find the reason for irregular or stopped menstrual periods.
- Confirm the start of menopause or perimenopause. Menopause is the time in a woman's life when her menstrual periods have stopped and she can't become pregnant anymore. It usually starts when a woman is around 50 years old. Perimenopause is the transition period before menopause. It can last for several years. LH testing may be done towards the end of this transition.
In men, these tests are most often used to:
- Help find the cause of infertility
- Find the reason for a low sperm count
- Find the reason for low sex drive
In children, these tests are most often used to help diagnose early or delayed puberty.
- Puberty is considered early if it starts before age 9 in girls and before age 10 in boys.
- Puberty is considered delayed if hasn't started by age 13 in girls and by age 14 in boys.
Why do I need an LH test?
If you are a woman, you may need this test if:
- You've been unable to get pregnant after 12 months of trying.
- Your menstrual cycle is irregular.
- Your periods have stopped. The test may be used to find out if you have gone through menopause or are in perimenopause.
If you are a man, you may need this test if:
- You've been unable to get your partner pregnant after 12 months of trying.
- Your sex drive is decreased.
Both men and women may need testing if they have symptoms of a pituitary disorder. These include some of the symptoms listed above, as well as:
- Weight loss
- Decreased appetite
Your child may need an LH test if he or she does not seem to be starting puberty at the right age (either too early or too late).
What happens during an LH levels test?
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for the test?
If you are a woman that has not gone through menopause, your provider may want to schedule your test at a specific time during your menstrual cycle.
Are there any risks to the test?
There is very little risk to having a blood test. You may have slight pain or bruise at the spot where the needle was put in, but most symptoms go away quickly.